A neuronal short circuit

As the sperm turns, success

Et cetera

A closer look at clot-busters

Cats and the pregnant woman

Brain scans reveal disruption in the neural circuitry of children with dyslexia

Using functional magnetic resonance imaging (fMRI), researchers led by a husband-and-wife team at Yale have found a neuronal short circuit in dyslexic children and identified an area of the brain that is linked to skilled reading. Their finding builds on a previous study that linked poor reading in adults with dyslexia to a specific region in the brain. “Because this finding coincides with findings in adults, it shows dyslexia is persistent,” said Sally E. Shaywitz, M.D., professor of pediatrics with an appointment in the Child Study Center and co-author of the study. “It shows there is an urgency for early intervention. And we were able to identify an area of the brain that correlates with skilled reading, the word-form area in the back of the left side of the brain.”

Shaywitz and her husband, Bennett A. Shaywitz, M.D., professor of pediatrics and neurology with an appointment in the Child Study Center, found that neural circuits in the word-form area, also known as the occipito-temporal area, are disrupted in children with dyslexia.

“By seeing the disruption on brain imaging it says to us as physicians and scientists that dyslexia is as real an entity as any other medical disorder,” said Bennett Shaywitz, co-principal investigator of the study and lead author of the paper in the July 15 issue of Biological Psychiatry. Also contributing to the work was John C. Gore, Ph.D., now at Vanderbilt University.

This study follows one in 1998 in which the Shaywitzes and colleagues found a disruption in posterior neural systems for reading in the brains of dyslexic adults. That finding begged a key question. “We did not know if this disruption was just the end result of years of poor reading or if it was there from the beginning of the time a child should be able to read, which is around 6 or 7 years old,” said Sally Shaywitz.

The team used fMRI to scan the brains of 70 dyslexic readers and 74 nonimpaired readers ages 7 to 18 while they performed reading tasks with real words and “pseudowords,” made-up words that the children were asked to pronounce. The tasks mimicked the problems dyslexic children face in sounding out words. The team found evidence of a functional disruption of the neural systems involved in skilled reading, confirming the hypothesis that the defect is present at a young age.

“We believe dyslexic children are born with this disruption,” Bennett Shaywitz said.

The nature and cause of the disruption are not clear. “That’s the next step,” he said. With colleagues at Yale, he’s using magnetic resonance spectroscopy to study brain cells in the region that is disrupted.

According to the Shaywitzes, about one in five children has dyslexia, which affects children without regard to level of intelligence. Typically, dyslexics compensate by using other parts of the brain to read.

“Instead of being able to develop systems in the back of the brain they develop systems in the front of the brain, but it is very laborious,” said Sally Shaywitz. “It’s not that they don’t learn to read at all, but it’s harder to read.”

Although symptoms appear as soon as children start to read, most dyslexic children are not diagnosed until they’re in the third grade, she said. “There is absolutely no question that the earlier a child is identified, the more difference you can make,” she said, adding that early placement in preventive and remedial programs can help children with dyslexia. The programs use exercises, games and rhymes to help dyslexic children break up words into their individual parts. “If you start at the beginning you can have a good chance of helping that child in an efficient way. What we think—and we have some evidence to support this—is that we can help the area of the brain that is disrupted.”

—John Curtis

As the sperm turns, success

Although intracytoplasmic sperm injection—in which a single sperm is placed inside a mature egg—increases the chances of a successful pregnancy, it also carries a risk of genetic abnormalities in children. Now two Yale scientists have devised a method for selecting genetically healthy sperm to lower those odds. Gabor B. Huszar, M.D., HS ’76, and Attila Jakab, M.D., found that healthy sperm develop a receptor that recognizes an acid in the female reproductive tract; they then devised a method of using the acid to identify the most robust candidates. Huszar and Jakab presented their work at the European Society of Human Reproduction and Embryology’s June meeting in Vienna.

—John Curtis

Et Cetera

A closer look at clot-busters

Clot-busting drugs are almost always administered to stroke patients incorrectly, sometimes with serious consequences, according to a recent Yale study.

Researchers reviewed the medical records of 63 patients who received thrombolytic therapy between 1996 and 1998. They found departures from recommended practice 97 percent of the time. “Major deviations from protocol were present in two-thirds of the cases and were associated with serious or fatal consequences,” said Dawn M. Bravata, M.D., principal investigator of the study published in the Archives of Internal Medicine.

Errors ranged from incorrect dosages and delays in administering the drugs to giving them to at-risk patients. Responsibility for the drugs’ misuse was widespread, the study found, and detours from protocol occurred all along the heath care pathway. Why? “It’s a hard drug to give properly,” Bravata said. “It’s not something doctors do every day.”

—Jennifer Kaylin

Cats and the pregnant woman

There’s good news and bad news for pregnant women who live with cats. On the up side, they face little risk of contracting toxoplasmosis from their feline companions. On the other hand, there’s one less reason to avoid cleaning the litter box.

Jeffrey D. Kravetz, M.D., an assistant clinical professor of medicine who has two cats, decided to review the literature about cat-related diseases after his wife became pregnant. He found that casual contact with a cat does not put a woman’s unborn child at risk. “It’s never been proven that toxoplasmosis (an infection that can cause miscarriages or damage to fetuses) comes from direct cat contact,” he said. According to Kravetz it’s much more likely a woman will get the infection by eating undercooked meat or digging with bare hands in contaminated soil.

Kravetz, whose review article appeared in the Archives of Internal Medicine in September, advises pregnant women who must change a litter box to do so daily, wear gloves and wash their hands afterwards. “Basically, use common sense and don’t worry,” he said.

—Jennifer Kaylin